rasterImage() and grid.raster() error out on empty raster

git-svn-id: https://svn.r-project.org/R/trunk@63974 00db46b3-68df-0310-9c12-caf00c1e9a41
doc tweaks

git-svn-id: https://svn.r-project.org/R/trunk@63975 00db46b3-68df-0310-9c12-caf00c1e9a41
update info

git-svn-id: https://svn.r-project.org/R/trunk@63977 00db46b3-68df-0310-9c12-caf00c1e9a41
easier to report 250Kb

git-svn-id: https://svn.r-project.org/R/trunk@63979 00db46b3-68df-0310-9c12-caf00c1e9a41
report is all example times < 0.01s

git-svn-id: https://svn.r-project.org/R/trunk@63980 00db46b3-68df-0310-9c12-caf00c1e9a41
more on Mac TeX distributions

git-svn-id: https://svn.r-project.org/R/trunk@63982 00db46b3-68df-0310-9c12-caf00c1e9a41